Paragathotanais abyssorum, Larsen, Kim, 2007

Larsen, Kim, 2007, Family Agathotanaidae Lang, 1971 a *, Zootaxa 1599, pp. 41-60 : 49-54

Paragathotanais abyssorum n. sp.

Figures 6–9

Material examined. Holotype, ovigerous female ( KMNH IvR 500.165), station TD-8, 39°15.54’– 39°17.01’N, 144°45.37’– 144°42.46’E. 5762–5733 metres, 29 September 2001. Paratypes: 1 male (damaged) same locality. 3 non-ovigerous females, 1 male, 2 mancae ( KMNH IvR 500.166), same locality.

Diagnosis, female. Pereonite shoulder well demarcated. Antenna with five articles; article 3 without distal fusion line. Pereopods 4–6 propodus with double row of distal spines; dactylus without spines. Male. As female except antennule wider. Only double row of spines on pereopod 4–5. Pleonites with pleopods.

Etymology. Name derived from the deep-sea habitat.

Description, adult female.

Body ( Fig. 6 A,B): 7.5 times as long as broad.

Cephalothorax. Marginally shorter than combined length of pereonites 1 and 2, almost rectangular.

Pereonites. Pereonite shoulder well demarcated. Pereonites 1 and 6 wider than long. Pereonite 2 length subequal in width. Pereonites 3, 4 and 5 longer than wide.

Pleon. All pleonites subequal and narrower than pereonites and pleon. Pleotelson with dorsal distal plate and blunt apex.

Antennule ( Fig. 6 C). With four articles. Length shorter than cephalothorax. Article 1 longer than rest of antennule, with one simple and one setulated setae. Article 2 longer than article 4, with two simple distal setae. Article 3 band-shaped and shorter than other articles, with one simple distal seta. Article 4 less than three times article 1, with three simple distal setae and one aesthetasc.

Antenna ( Fig. 6 D). With five articles. About as long as antennule article 1. Article 1 wider than other articles, with one dorsodistal seta. Article 2 band-shaped, naked. Article 3 longer than combined length of other antenna articles, without fusion line, with one distal simple seta. Article 4 longer than article 2, tapering and with one simple distal seta. Article 5 minute with one distal seta and one aesthetasc.

Mouthparts. Labrum ( Fig. 6 E) with flat setose distal edge. Left mandible ( Fig. 6 F) lacinia mobilis short and shaped as a blunt spine, incisor broad and bifurcate, molar thin and tapering. Right mandible ( Fig. 6 G) incisor broader than on left mandible, with three denticles. Labium ( Fig. 6 H) lobes tapering distally, with distal setules. Maxillule ( Fig. 6 I) endite with nine distal spiniform setae, palp lost during dissection. Maxilla ( Fig. 6 J) small and featureless. Maxilliped ( Fig. 6 K) endites without setae. Palp article 1 naked; article 2 with three inner setae. Article 3 with three inner setae. Article 4 with five distal setae. Epignath not recovered (see male).

Cheliped ( Fig. 6 L). Basis shorter but wider than merus. Merus triangular, with one ventral seta. Carpus as long as propodus including fixed finger, with one medio-dorsal, one dorso-distal and one ventral setae, with small carpal shield. Propodus with one seta at dactylus insertion. Fixed finger with one ventral seta, three setae and one distal denticle on inner margin. Dactylus as long as fixed finger.

Pereopod 1 ( Fig. 7 A). Coxa naked. Basis shorter than combined length of the four succeeding articles, naked. Ischium with one ventral seta. Merus shorter than carpus, widening distally, with one spiniform ventral seta. Carpus shorter than propodus, rectangular, with two spiniform distal setae. Propodus about half as long as basis, with one long and one spiniform ventro-distal setae and dorsal spine. Dactylus and unguis combined as long as propodus, unguis without distal processes.

Pereopod 2 ( Fig. 7 B). As pereopod 1 except coxa with one seta and propodus without long seta. Pereopod 3 ( Fig. 7 C). As pereopod 2.

Pereopod 4 ( Fig. 7 D). Basis not wider than on pereopods 1–3, apparently naked but with medial process (which usually contains a sensory seta, suggesting this has been lost during handling). Ischium with one ventral seta. Merus with two spiniform setae, shorter than carpus. Carpus with three spiniform and one simple distal setae. Propodus with three long (longer than half of dactylus/unguis), distal spiniform setae, dorsal spine, and two rows of spines. Dactylus and unguis combined longer than propodus, dactylus without spines.

Pereopod 5 ( Fig. 7 E). As pereopod 4 except basis without process.

Pereopod 6 ( Fig. 7 F). A as pereopod 4 except coxa with one seta.

Pleopods lacking in females.

Uropods ( Fig. 6 M). Basal article wider but shorter than endopod. Exopod process obvious, with one short and one long simple distal setae. Endopod with four long simple distal setae.

Description of male, (where differing from female).

Body ( Fig 8 A). Pleon wider than in female.

Antennule ( Fig. 8 B). With traces of fifth terminal article. Wider than in female.

Epignath ( Fig. 8 K). Naked, terminal spine absent.

Pereopod 4 ( Fig. 9 D). Propodus spines not as prominent as in female.

Pereopod 6 ( Fig. 9 F). Propodus spines absent.

Pleopods ( Fig. 8 M). All pairs similar, with short, stiff, simple setae only. Held in a cone but not coalescent. Endopod with nine distal setae, exopod with nine distal and one subdistal setae.

Remarks. This species is fairly easily recognizable from other species in the genus by the distal propodal spination of pereopods 4–6 and lack of dactylus spines. The male completely lacks the propodal spines on pereopod 6 while these are prominent on pereopod 5 and less prominent on pereopod 4. The reason for such variation is not clear.

Figures

FIGURE 6. Paragathotanais abyssorum n. sp., female. A, holotype, dorsal view; B, paratype, lateral view; C, antennule; D, antenna; E, labrum; F, left mandible; G, right mandible; H, labium; I, maxillule; J, maxilla; K, maxilliped; L, cheliped; M, uropod. Scale bar habitus 0.5 mm, other scale bar = 0.1 mm.

FIGURE 7. Paragathotanais abyssorum n. sp., female, paratype. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bar = 0.1 mm.

FIGURE 8. Paragathotanais abyssorum n. sp., male, paratype. A, lateral view; B, antennule; C, antenna; D, labrum; E, left mandible; F, right mandible; G, labium; H, maxillule; I, maxilla; J, maxilliped; K, epignath; L, cheliped; M, pleopod; N, uropod. Scale bar habitus 0.5 mm, other scale bar = 0.1 mm.

FIGURE 9. Paragathotanais abyssorum n. sp., male, paratype. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bar = 0.1 mm.